THE SIR SUPPLIED US WITH 5G OF 15N FOR OUR PROJECT WHICH IS THE PREPARATION UNIFORMLY 15N, 13C ENRICHED OLIGONUCLEOTIDE AS FOLLOWS: A PUC PLASMID CONTAINING YEAST REPLICATION ORIGIN (ARS1) WAS KINDLY PROVIDED BY J. DIFFLEY. THE HOST CELL FOR THE PLASMID IS E. COLI STRAIN K567. THE CELLS WERE GROWN IN M9 MINIMAL MEDIA CONTAINING 99% 13C ENRICHED GLUCOSE (ISOTEC) AND/OR 99% 15N ENRICHED AMMONIUM SULFATE (LOS ALAMOS STABLE ISOTOPE RESOURCE) AS THE SOLE CARBON OR NITROGEN SOURCES, RESPECTIVELY. THE LABELED PLASMID WAS THEN EXTRACTED AND PURIFIED FROM CRUDE CELL EXTRACTS. THE FRAGMENT DNA OLIGO CONTAINING ARS1 WAS RELEASED FROM THE VECTOR PLASMID BY RESTRICTION DIGESTIONS. THE FURTHER PURIFICATION OF THE OLIGO WAS ACCOMPLISHED BY HPLC. BY USING THIS NOVEL METHOD DEVELOPED IN OUR LAB, WE ARE ABLE TO OBTAIN A LABELED OLIGO WITH HIGH PURITY.